[Eeglablist] re-reference with EGI data

[Joshua Hartshorne]

Thanks, Stephen, Tarik, Simon,

I am using the older GSN (pre-HydroCel) caps. EEGLab seems to correctly
decide which locations file to use, and that file matches the one on EGI's
website.

I did notice, however, an odd warning when importing, which makes me
worried and makes me wonder if any of you know something about it.
Invariably, I get this message:

eeg_checkset warning: 3rd dimension size of data (1) does not match the
number of epochs (0), corrected
eeg_checkset warning: number of columns in data (501045) does not match the
number of points (0): corrected

Here is all the output, just so you can see that warning in context:

 Removing trailing character of selected file to find base file name

Base file name is:
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20001.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20002.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20003.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20004.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20005.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20006.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20007.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20008.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20009.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20010.raw

Importing binary EGI data file ...

Importing
/Users/jkh80/Documents/EEG_Data/ScalarImplicature/SI_Filtered_Raw/SI20011.raw

pop_chanevent: importing events from data channel 166 ...

eeg_checkset warning: 3rd dimension size of data (1) does not match the
number of epochs (0), corrected

eeg_checkset warning: number of columns in data (991630) does not match the
number of points (0): corrected

eeg_checkset note: upper time limit (xmax) adjusted so (xmax-xmin)*srate+1
= number of frames

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 165 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 164 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 163 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 162 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 161 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 160 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 159 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 158 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 157 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 156 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 155 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 154 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 153 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 152 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 151 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 150 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 149 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 148 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 147 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 146 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 145 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 144 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 143 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 142 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 141 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 140 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 139 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 138 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 137 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 136 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 135 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 134 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 133 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 132 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 131 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

pop_chanevent: importing events from data channel 130 ...

eeg_checkset note: creating the original event table (EEG.urevent)

Removing 1 channel(s)...

Deleting empty data reference channel (reference channel location is
retained)

EGI channel location automatically detected GSN129.sfp ********* WARNING
please check that this the proper file



The data end up looking reasonable, so I'm not too worried about this, but
I'd like to make sure it's not something I should worry about.

Thanks,

Josh


On Wed, Aug 29, 2012 at 2:49 PM, Simon-Shlomo Poil <
poil.simonshlomo at gmail.com> wrote:

> Dear Joshua,
>
> This is known issue with the EGI electrode files. You simply need to
> delete the additional channels.
>
> Try to use one of the two channel location files I have attached. However,
> first carefully check that the layout is the same as your cap (EGI has
> different layouts!).
>
> Hope it works,
> Simon
>
> --
> Simon-Shlomo Poil
> http://www.nbtwiki.net
>
> 2012/8/24 Joshua Hartshorne <jkhartshorne at gmail.com>
>
>> I have EGI data recorded with a 128 electrode cap (vertex reference). I
>> exported it to EEGLab and included the reference in the export (I used the
>> multiple file format).
>>
>> EEGLab seems to recognize everything fine and includes 128 electrodes in
>> the data, though when I go to "edit channel locations", I see 132 channels.
>> The last one is my reference channel, labeled correctly as Cz. Though it's
>> channel type is listed as "REF", no Reference is listed in the pop-up
>> window (the section below the panel of "channel type") for any channel. I
>> have no idea what channels 129-131 are (they are labeled FidNz, FidT9, and
>> FidT10).
>>
>> So I want to re-reference. If I check "compute average reference", I
>> don't have the option of retaining the old reference channel, which seems
>> odd. If I click on the "..." button after "Add current reference channel
>> back to the data", I get an error (??? Error using ==> waitfor Error while
>> evaluating uicontrol Callback). From the wiki, I understand I should have
>> gotten a list. Manually setting reference to "Cz" or "132" using the "edit
>> channel info" window for channels 1:128 doesn't fix this problem.
>>
>> However, if I leave all that blank, I "successfully" re-reference to
>> average reference. That is, I don't get an error, though I'm not sure how
>> to determine whether it worked correctly or not.
>>
>> What I'd really like to do is re-reference to the average of the mastoids
>> (channels 57 and 101), which would aid comparison with another dataset that
>> was collected on different equipment with fewer electrodes. But the wiki
>> suggests that I have to do this by going through average reference first
>> (really?), so I wanted to make sure I had that much right first.
>>
>> In any case, I assume that if I list two electrodes in the "re-reference
>> data to channel(s):" box that it will automatically compute the average of
>> those two. I tried doing that (both with and without going through average
>> reference), and I notice that channels 57 and 101 are *not* listed as "REF"
>> in "Channel type" after doing this, while Cz is still listed as "REF",
>> though "Reference" is now listed as "E57 E101".
>>
>> I appreciate any help.
>> Josh Hartshorne
>>
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>
>
>
> --
>
>  <http://www.kispi.uzh.ch/Kinderspital/Medizin/mrzentrum_en.html>
>
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